Coaxial connector

ABSTRACT

A coaxial cable connector featuring inner and outer ferrules between which the outer conductor of a semi-rigid cable is squeezed. The assembly of the connector onto the cable is accomplished with ordinary standard hand wrenches operating on an outer coupling containing the outer ferrule nut threadedly engaging a connector body containing the inner ferrule. The structure of the connector preserves the critical diameters of the coaxial cable thereby reducing or eliminating reflective loss of radio frequency energy.

United States Patent [191 Forney, J r.

[ 1 Dec. 11, 1973 COAXIAL CONNECTOR [75] Inventor: Edgar Wilmot Forney,Jr.,

Harrisburg, Pa. [73] Assignee: AMP Incorporated, Harrisburg, Pa.

[22] Filed: May 12, 1972 [21] Appl. No.: 252,791

[521 U.S. C1. 174/88 C, 174/89, 339/89 C, 339/177 R [51] lnt. Cl ..1l02g15/08 [58] Field 01 Search 174/88 C, 75 C, 89;

339/177 R, 177 E, 89 C [56] References Cited I UNITED STATES PATENTS2,296,766 9/1942 Bruno 339/177 R 2,328,469 9/1943 Laffly 174/893,551,882 12/1970 OKeefe 174/75 C 3,184,706 5/1965 Atkins 174/89 X3,469,014 9/1969 Papadopulos 174/89 X 2,995,388 9/1961 Morello, Jr. etal. 174/88 C X 3,245,027 4/1966 Ziegler, Jr 174/88 C X 3,701,086 10/1972Somerset R 3,492,604 1/1970 Fan X 3,498,647 3/1970 Schroder 339/177 R XPrimary ExaminerBernard A. Gilheany Assistant ExaminerA. T. GrimleyAtt0rneyWilliam J. Keating et al.

[57] ABSTRACT 8 Claims, 6 Drawing Figures SHEET 10? 2 PATENTEU DEC 1]1975 PAIENIEDUEC n ma 3778535 sum 2 OF 2 COAXIAL CONNECTOR BACKGROUND OFTHE INVENTION Semi-rigid coaxial cables have been developed for handlingradio and ultrahigh frequency energy. Such cables typically have acenter copper conductorand aluminum outer shield with air alarge part ofthe dielectric medium thereinbetween. These. conductors or cables arelight weight and are'especially suitable for use in cable televisionsystems. However, considerable difficulty has been experienced indeveloping a suitable connector for terminating the coaxial cable.,Moreparticularly, difficulty is experiencedin securing the connectorshell to the cable shield with sufficient strength so that the two willnot separate underphysicalloads or fail under thermal cycling which arenormal in actual field operations.

In general, workers in the field have developed several approaches interminating coaxial cable. One approach has been to provide-a clamp orcollet having interior teeth which are driven into the .outer conductorso as to provide the mechanical gripping action.

The approach noted above and other similar approaches well known tothose skilled in theart possess some drawbacks. The first is that-theouter cable conductor is unsupported by the relatively weak cabledielectric at the clamping point so thatit-begins to collapse underload, i.e.,. itreduces radiallyso-that the electrical and mechanicalconnectionto theconnector body deteriorates.

In order to counter the collapse of'the outer conductor under clampingpressure a practicewas developed to insert a sleeve orferrule within andnext to the outer cable conductor toprovide support. Thishelpedthecollapsing problem considerably but introduced another problem; thecharacteristic impedance of a coaxial cable is a function of the innerdimensions; thus, by inserting the ferrule into the cable,,the impedanceat this point is changed and there is a reflective loss -in thefrequency energybeing transmitted.

Accordingly, the present invention provides a device for terminating orconnecting semi-rigid coaxial cable of the type having a centerconductor surrounded by a dielectric medium and an outer conductorhaving a given inner diameter held to agiven close tolerance forefficient signal transfer, which comprises a threaded insert assemblywhich includes a coupling nut having external threads on one end and twolongitudinal concentric bores therein, one of the bores being largerthan the second, a outer ferrule having a sleeve portion and radiallyextending rim portion, the sleeve portion .adapted to slide into thecoupling nut, and a retaining ring having teeth on the inner edges, thering adapted to fit onto the cable, and.an adapter assembly whichincludes a connector body having .intemal threads adapted to receive theexternal threads on the coupling nut, .and also having three,longitudinal, concentric bores of differingdiameters, and'a innerferrule having a beveled end, the ferruleadapted to'be vhoused in one ofthe bores in the connector body and further adapted to be inserted intoaendof the cablewhen the coupling nut and connector body are threadedlyjoined.

BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 1 illustrates a-CATV directionaltap to .which semi-rigid coaxial cable is connected utilizing thepresent invention;

FIG. 1A shows details of the coaxial cable of FIG. 1;

FIG.2 is a perspective, exploded and partially sectioned view of onehalf of the connector construction in accordance with the presentinvention;

FIG. 3 is a perspective exploded and partially sectioned view of anotherhalf of the connector constructed in accordance with the presentinvention; and

FIGS. 4 and 5 illustrate the assembly of the connector shown in FIGS. 2and 3 to a coaxial cable.

DESCRIPTION OF THE PREFERRED EMBODIMENT A CATV directional tap,designated at 10 in FIG. 1, .is used, either on over-head lines orunderground, to provide television signals, entering therein fromdistribution coaxial cable 12 attached thereto via coaxial vconnector14,to the homes located along the TV cable. Tap 10 is a conventionaldirectional coupler and splitter such as manufactured by JerroldElectronics, Inc. In the modelshown in FIG. 1, tap 10 contains acircuitry -(not,shown).which sends the TV signals into .four differenthomes via house tapslS (of which only two are seen).

Cable 12 is one type of semi-rigid coaxial cable whose structure can beseen in FIG. 1A. The cable includes an outer conductor 16 and a centerconductor .18. The dielectric material separating the two conductors isairv filled chamber, designated at 20, thereinbe- .tween. Disks 22 ofdielectric material such as polyethylene arepositioned at spacedintervals along the inside of cable 12, to support and centralize centerconductor As is well known, one of the critical dimensions in coaxialcable such as cable 12 is the diameter of the inner surface of outerconductor16 shown as D in FIG. 1A.

It is very important to avoid or at least minimize any change in thisdimension. Where a change results in a mismatch of cable impedance andfrom that a reflective loss of radio frequency (R.F.) energy.

In accordance with the inventive concept a termination of coaxial cable12 shown in FIG. 1A is provided through coaxial connector 14 whicheliminates damaging deformation to cable 12 and which provides a meansfor attaching cable 12 to tap 10 without the use of special tools.Coaxial connector 14 is shown in detail in FIGS. 2 and 3 to whichreference is now made.

FIG. 2 shows threaded insert assembly 24 of coaxial connector 14. Theassembly includes a housing or coupling nut 26, outer ferrule 28 andcable retaining ring 30. FIG. 2 also shows guage 32 which is provided toinsure proper installation of connector 14 onto cable 12 aswill-bedescribed in detail below.

Coupling nut 26 contains external threads 34 on end 35, and a hexagonalsurface 36 on end 37. Internally, coupling nut 26 defines two concentricbores of differing diameters. The smallest diameter bore 38, beginningattend 37, meets the largest diameter bore 40 which begins at end 35.The diameter of smallest bore 38 is slightly greater than the outerdiameter of outer ferrule 28.

Outer ferrule 28 consists of a sleeve 44 and a rim 46.

.Sleeve.44 is thin walled and is slightly longer than coupling nut 26.Rim 46extends outwardly for a distance slightly less than the rootdiameter of external threads '34 on coupling nut 26. Internally, outerferrule 28 defines .a bore .48, andwithin rim 46 a internal, annularrecess having .a step 51. The diameter of bore 48 is slightly greaterthan the outer diameter of coaxial cable 12 and the diameter of recess50 within step 51 is sized to receive therein cable retaining ring 30.

Cable retaining ring 30 is characterized by having serrations or springfingers 52 on its inner edge 54. The inner diameter of ring 30 with theinner spring fingers 52 in a nondeformed position is slightly less thanthe outer diameter of coaxial cable 12. The outer diameter of ring 30 isslightly smaller than the diameter of groove 50 located in outer ferrule28.

Guage 32 is a thin-walled plastic or heavy paper collar whose innerdiameter is only large enough to allow the collar to he slipped overthreads 34 on coupling nut 26.

FIG. 3 shows feed-through adapter assembly 58 of coaxial connector 14.The assembly includes an inner ferrule 60 and connector body 62.

Inner ferrule 60 is a thin-walled cylinder whose forward or leading end'64 (toward the left of the drawing) is beveled inwardly. The outerdiameter of innerferrule 60 other than beveled end 64 is slightlygreater than inner diameter D of coaxial cable 12.

. Connector body62 contains external threads 66 on one end which aresized to be received by internal threads (not shown) in tap 10. Further,connector body 62 has a hexagonal surface 68 to facilitate assembly viaa standard wrench. A recess 70, located between threads 66 and surface68, is provided to receive O-ring 72. Internally, connector body 62defines three concentric bores of differing diameters. The largestdiameter bore is 74 and it contains internal threads 76 which mate withexternal threads 34 on coupling nut 26. A recess 78, located immediatelyadjacent to threads 76, receives O-ring 80. The next larger diameterbore is 82 and where it meets bore 74 a shoulder 84 is formed. Thecorner between bore 82 and shoulder 84 has been beveled as shown at 86.The diameter of bore 82 is large enough to accommodate inner ferrule 60therein. The smallest diameter bore is 88 and whereit meets bore 82,shoulder 90 is formed. Shoulder 90 is of the same thickness as innerferrule 60 and the diameter of bore 88 equals the inner diameter ofinner ferrule 60.

ASSEMBLY OF THE PREFERRED EMBODIMENT FIGS. 4 and 5 illustrate theassembly of coaxial connector 14 onto coaxial cable 12.

Prior to assembly on cable, outer ferrule 28 is inserted into couplingnut 26 to where rim 46 abuts against end 35 of the coupling nut. Theportion of sleeve 44 which extends beyond end 37 of coupling nut 26 isflared outwardly as shown ,in FIG. 4 so that the outer ferrule cannotmove longitudinally but can move rotationally. Cable retaining washer 30is inserted into recess 50 in rim 46, coining over step 51 to lock thering in place. Guage 32 is slid over threads34 on coupling nut 26.

Connector body 62, with inner ferrule 60 staked into an interference fitin bore 82, is threaded onto coupling nut 26 as far as guage 32 permits.

Coaxial cable 12 is then inserted into the partial assembly describedabove until touching contact is made with inner ferrule 60. At thatpoint the cable cannot be slid further in without considerable forcethus alerting the assembler that the cable has been pushed through cableretaining washer 30 the optimum distance. As the cable is pushed in, theinwardly extending spring fingers 52 tightly graspwasher 30 around thecable thereby looking it in threaded insert assembly 24.

Connector body 62 is now backed off coupling nut 26. Feed throughadapter assembly'58 may now be attached to a cable televisiondirectional tap 10 via external threads 66 and internal threads (notshown) on the tap as seen in FIG. 1 on the right side of tap 10. O-ring72 seals the attachment in a manner well known in the art.

With reference to FIG. 5, final assembly of coaxial connector 14 takesplace when threaded insert assembly 24, with coaxial cable 12 attachedthereto via the manner disclosed above and with guage 32 removed, isthreadedly attached to feed through adapter assembly 58. As coupling nut26, which can rotate freely about outer ferrule 28 and cable 12 attachedthereto, is threaded into connector body 62, inner ferrule 60 entersinside outer conductor 16 and begins to spread it radially outwardly,beveled end 64 aiding in a manner well known in the art. As the innerferrule is advanced farther into the cable, the outer conductor issqueezed against rim 46 where it becomes thinned; i.e., the outerconductor is longitudinally extruded in either direction away from therim. In addition, both a portion of sleeve 44 and outer conductor 16 isexpanded radially outwardly into bore 40 in coupling nut 26 with the netresult that the inner diameter of the outer conductor is maintainedthrough coaxial connector 14 and coaxial cable 12 is securely attachedthereto without sever deformation as would occur in a clamp or crimptype connection.

As coupling nut 26 bottoms out clamping rim 46 to connector body 62,O-ring seals the connector against entry of water along the threads asseen in FIG. 5. A metal-to-metal seal in the expanded area of sleeve 44and outer conductor 16 prevents water entry along the outer cableconductor.

A novel feature of the present invention is that assembly of connector14 is accomplished entirely with only standard wrenches; no specialtools such as hand crimping devices are needed.

As is now apparent, the assembly is quick, sure and uncomplicated sothat only simple installation instructions are required.

Another novel feature of the present invention is that the coaxialconnector disclosed herein maintains the characteristic impedance of thecoaxial cable to which it is attached.

Though the invention has been described with respect to a specificpreferred embodiment thereof, many variations and modifications thereofwill immediately become apparent to those skilled in the art. It istherefor the intention that the appended claims be interpreted asbroadly as possible in view of the prior art to include all suchvariations and modifications.

What is claimed is:

l. A connector for terminating a semi-rigid coaxial cable of the typehaving a center conductor surrounded by a dielectric medium and an outerconductor having a given inner diameter, which comprises:

a. a insert assembly comprising 1. a coupling nut having externalthreads on one end and a longitudinal bore therethrough,

' 2. an outer ferrule adapted to receive said cable, said ferrule havinga sleeve and on one end of said sleeve a radially extending rim, saidrim having a inwardly facing recess, said sleeve adapted to bepositioned in said bore in said coupling nut, 3. A connector forterminating a semi-rigid coaxial 3. a retaining ring having teeth on theinner edge, cable for the propogation of high frequency signals,

said ring positioned in said recess in Said rim and said coaxial cablehaving a metallic tubular outer conadapted to fit onto said cablewhereby said teeth d t hi h omprises;

p Said Cable; and 5 a. an outer ferrule adapted to receive an end ofsaid an adapter assembly comprising coaxial cable inserted therein;

an inner ferrule adapted to be inserted into Said b. an inner ferruleadapted to be driven into an end cable i inner ferrule hailing an innerdiameter of said coaxial cable whereby said outer conductor substannanyequal to the diameter of Said is pressed radially against said outerferrule; and

outer conductor; 1

2. a connector body having a passageway therethrough with a portiontherein adapted to receive said inner ferrule and internal threads atone end adapted to threadedly receive said insert assembly whereby assaid coupling nut threadedly engages said connector body, said innerferrule is driven into said cable positioned within said outer ferrulethereby expanding said outer conductor against said outer ferrule.

2. A connector to connect an end of a semi-rigid cable to a cabletelevision directional tap or the like, said connector comprising:

a. an inner ferrule having a beveled end, said ferrule c. housing meansto contain said outer and inner ferrules.

4. The connector of claim 3 wherein the inner diameter of said innerferrule substantially equals the inner diameter of said metallic tubularouter conductor.

5. The connector of claim 3 wherein said outer ferrule has a deformableinelastic sleeve portion whereby as said inner ferrule presses saidouter conductor outwardly and radially, said outer conductor and saidsleeve portion surrounding said conductor are deformed outwardly andradially.

6. The outer ferrule of claim 5 wherein a rim is posi tioned at one endof said sleeve portion and as said adapted to be inserted into the endof Said cable, inner ferrule presses said outer conductor thereagainst,b. a first housing adapted to hold said inner ferrule, Sald outerconductor exirlldes f lY- c. an outer ferrule adapted to receive saidcable in- T fonnector of F 3 whereln 531d means to d therethrough,contain said outer and inner ferrules includes: (1. a ring havingserrations on its inner edge and a couplmg nut adapted to Comm" 531dOuter adapted to slide over the end of said cable protrud- Yule thefeln;and i th h id outer f l id serrations b. a connector body adapted tocontain said inner adapted to engage said cable, ferrule and furtheradapted to receive said coupling e. a second housing adapted to receivesaid outer ferrule and ring and further adapted to mate with said 8. Thecoupling nut of claim 7 wherein said outer ferfirst housing whereby saidinner ferrule is driven rule is rotatably mounted therein. into said endof said cable.

1. A connector for terminating a semi-rigid coaxial cable of the typehaving a center conductor surrounded by a dielectric medium and an outerconductor having a given inner diameter, which comprises: a. a insertassembly comprising
 1. a coupling nut having external threads on one endand a longitudinal bore therethrough,
 2. an outer ferrule adapted toreceive said cable, said ferrule having a sleeve and on one end of saidsleeve a radially extending rim, said rim having a inwardly facingrecess, said sleeve adapted to be positioned in said bore in saidcoupling nut,
 3. a retaining ring having teeth on the inner edge, saidring positioned in said recess in said rim and adapted to fit onto saidcable whereby said teeth grip said cable; and b. an adapter assemblycomprising
 1. an inner ferrule adapted to be inserted into said cable,said inner ferrule having an inner diameter substantially equal to theinner diameter of said outer conductor;
 2. a connector body having apassageway therethrough with a portion therein adapted to receive saidinner ferrule and internal threads at one end adapted to threadedlyreceive said insert assembly whereby as said coupling nut threadedlyengages said connector body, said inner ferrule is driven into saidcable positioned within said outer ferrule thereby expanding said outerconductor against said outer ferrule.
 2. an outer ferrule adapted toreceive said cable, said ferrule having a sleeve and on one end of saidsleeve a radially extending rim, said rim having a inwardly facingrecess, said sleeve adapted to be positioned in said bore in saidcoupling nut,
 2. A connector to connect an end of a semi-rigid cable toa cable television directional tap or the like, said connectorcomprising: a. an inner ferrule having a beveled end, said ferruleadapted to be inserted into the end of said cable, b. a first housingadapted to hold said inner ferrule, c. an outer ferrule adapted toreceive said cable inserted therethrough, d. a ring having serrations onits inner edge and adapted to slide over the end Of said cableprotruding through said outer ferrule, said serrations adapted to engagesaid cable, e. a second housing adapted to receive said outer ferruleand ring and further adapted to mate with said first housing wherebysaid inner ferrule is driven into said end of said cable.
 2. a connectorbody having a passageway therethrough with a portion therein adapted toreceive said inner ferrule and internal threads at one end adapted tothreadedly receive said insert assembly whereby as said coupling nutthreadedly engages said connector body, said inner ferrule is driveninto said cable positioned within said outer ferrule thereby expandingsaid outer conductor against said outer ferrule.
 3. a retaining ringhaving teeth on the inner edge, said ring positioned in said recess insaid rim and adapted to fit onto said cable whereby said teeth grip saidcable; and b. an adapter assembly comprising
 3. A connector forterminating a semi-rigid coaxial cable for the propogation of highfrequency signals, said coaxial cable having a metallic tubular outerconductor, which comprises: a. an outer ferrule adapted to receive anend of said coaxial cable inserted therein; b. an inner ferrule adaptedto be driven into an end of said coaxial cable whereby said outerconductor is pressed radially against said outer ferrule; and c. housingmeans to contain said outer and inner ferrules.
 4. The connector ofclaim 3 wherein the inner diameter of said inner ferrule substantiallyequals the inner diameter of said metallic tubular outer conductor. 5.The connector of claim 3 wherein said outer ferrule has a deformableinelastic sleeve portion whereby as said inner ferrule presses saidouter conductor outwardly and radially, said outer conductor and saidsleeve portion surrounding said conductor are deformed outwardly andradially.
 6. The outer ferrule of claim 5 wherein a rim is positioned atone end of said sleeve portion and as said inner ferrule presses saidouter conductor thereagainst, said outer conductor extrudeslongitudinally.
 7. The connector of claim 3 wherein said means tocontain said outer and inner ferrules includes: a. a coupling nutadapted to contain said outer ferrule therein; and b. a connector bodyadapted to contain said inner ferrule and further adapted to receivesaid coupling nut.
 8. The coupling nut of claim 7 wherein said outerferrule is rotatably mounted therein.